In a cellular orthogonal frequency division multiplexing (OFDM) radio packet communication system, uplink and downlink data packet transmissions are transmitted via a subframe unit. A subframe is defined as a predetermined time period including a plurality of OFDM symbols. Currently, various control information for uplink/downlink data packet transmissions are also transmitted. Such control information includes information necessary for transmitting and receiving the uplink/downlink data packets, such as radio resource information used for transmitting and receiving the uplink/downlink data packets, a coding scheme, and a modulation scheme, for example. The control information is transmitted using at least one of the plurality of OFDM symbols included in the subframe.
A plurality of mobile terminals may communicate through one base station in a cellular OFDM radio packet communication system. Accordingly, scheduling for allocating radio resources for each of the plurality of mobile terminals is required. In particular, for a downlink control channel transmission, control information for the plurality of mobile terminals may be transmitted together. Thus, scheduling for allocating radio resources for the control information transmission is also required. Therefore, such scheduling information is also transmitted.
Among the plurality of OFDM symbols included in the subframe, the number of OFDM symbols used in transmitting the control information and/or the scheduling information may be varied per subframe according to a communication environment, the amount of control channel information, and the amount of scheduling information, etc. Thus, such information should be informed to a receiver. If errors occur in receiving the control information and the scheduling information, it is quite probable that errors occur in receiving the data of the corresponding subframe. Accordingly, what is needed is a system that overcomes the deficiencies of the prior art, such that control information and scheduling information can be decoded with a high success rate.